In general, plasticizers are based on corresponding esters produced through reaction of alcohols with polycarboxylic acids such as phthalic acid or adipic acid. Examples of commercially essential plasticizers include adipates of C8, C9 and C10 alcohols such as di(2-ethylhexyl) adipate, diisononyl adipate and diisodecyl adipate; and phthalates of C8, C9 and C10 alcohols such as di(2-ethylhexyl) phthalate, diisononyl phthalate and diisodecyl phthalate.
Meanwhile, plasticizers should be suitably selected according to UL (Underwriters Laboratories) heat resistance grade in order to produce wires (cables), automobile sheets and the like requiring heat resistance as a physical property.
For example, in case of PVC compounds for UL cables, a plasticizer, a filler, a flame retardant, a heat stabilizer or the like is blended with a PVC resin according to tensile strength, elongation, cold resistance and the like which are properties required to meet UL cable standards (grades).
The type of plasticizer used depends on heat-resistance grade. Specifically, plasticizers such as dioctyl phthalate (DOP), diisodecyl phthalate (DIDP) and diisononyl phthalate (DINP) are commonly used for 80 to 90° C. heat-resistance grade, and plasticizers such as trioctyl trimellitate (TOTM) and triisononyl trimellitate (TINTM) are used for 105° C. heat-resistance grade.
However, these plasticizers have superior heat resistance, but have a disadvantage of poor compatability.
In addition, a resin used also depends on heat-resistance grade of cables. More specifically, inexpensive PVC is generally used for products requiring heat resistance of 105° C. or less, and polyolefins such as polyethylene (PE) and thermoplastic elastomers (TPE) are generally used for products requiring heat resistance of 105 to 150° C.
In particular, for preparation of a polyethylene compound, unlike PVC, addition of a flame retardant is required, since polyethylene does not have flame retardancy, and a cross-linking agent is required for irradiation. That is, the polyethylene compound is prepared by adding carbon black to polyethylene and adding a plasticizer, a cross-linking agent, a flame retardant or the like thereto, followed by stirring and injection molding.
Accordingly, there is still a need for a plasticizer having heat resistance and superior compatability (workability) and a heat-resistant resin composition comprising the same.